Re: [Qemu-devel] [PATCH v4 2/8] acpi: add vmcoreinfo device

[Michael S. Tsirkin]

On Fri, Jul 14, 2017 at 08:20:05PM +0200, Marc-André Lureau wrote:
> The VM coreinfo (vmcoreinfo) device is an emulated device which
> exposes a 4k memory range to the guest to store various informations
> useful to debug the guest OS. (it is greatly inspired by the VMGENID
> device implementation)
> 
> This is an early-boot alternative to the qemu-ga VMDUMP_INFO event
> proposed in "[PATCH 00/21] WIP: dump: add kaslr support".
> 
> A proof-of-concept kernel module:
> https://github.com/elmarco/vmgenid-test/blob/master/qemuvmci-test.c
> 
> Signed-off-by: Marc-André Lureau <address@hidden>
> Reviewed-by: Laszlo Ersek <address@hidden>

It worries me that the format of this seems completely undefined
except in the patchset cover letter.
I don't think we should merge this before it is.

> ---
>  include/hw/acpi/aml-build.h        |   1 +
>  include/hw/acpi/vmcoreinfo.h       |  37 +++++++
>  hw/acpi/aml-build.c                |   2 +
>  hw/acpi/vmcoreinfo.c               | 208 
> +++++++++++++++++++++++++++++++++++++
>  hw/i386/acpi-build.c               |  14 +++
>  default-configs/arm-softmmu.mak    |   1 +
>  default-configs/i386-softmmu.mak   |   1 +
>  default-configs/x86_64-softmmu.mak |   1 +
>  docs/specs/vmcoreinfo.txt          | 138 ++++++++++++++++++++++++
>  hw/acpi/Makefile.objs              |   1 +
>  10 files changed, 404 insertions(+)
>  create mode 100644 include/hw/acpi/vmcoreinfo.h
>  create mode 100644 hw/acpi/vmcoreinfo.c
>  create mode 100644 docs/specs/vmcoreinfo.txt
> 
> diff --git a/include/hw/acpi/aml-build.h b/include/hw/acpi/aml-build.h
> index 88d0738d76..cf781bcd34 100644
> --- a/include/hw/acpi/aml-build.h
> +++ b/include/hw/acpi/aml-build.h
> @@ -211,6 +211,7 @@ struct AcpiBuildTables {
>      GArray *rsdp;
>      GArray *tcpalog;
>      GArray *vmgenid;
> +    GArray *vmcoreinfo;
>      BIOSLinker *linker;
>  } AcpiBuildTables;
>  
> diff --git a/include/hw/acpi/vmcoreinfo.h b/include/hw/acpi/vmcoreinfo.h
> new file mode 100644
> index 0000000000..6a73bcd1b2
> --- /dev/null
> +++ b/include/hw/acpi/vmcoreinfo.h
> @@ -0,0 +1,37 @@
> +#ifndef ACPI_VMCOREINFO_H
> +#define ACPI_VMCOREINFO_H
> +
> +#include "hw/acpi/bios-linker-loader.h"
> +#include "hw/qdev.h"
> +
> +#define VMCOREINFO_DEVICE           "vmcoreinfo"
> +#define VMCOREINFO_FW_CFG_FILE      "etc/vmcoreinfo"
> +#define VMCOREINFO_ADDR_FW_CFG_FILE "etc/vmcoreinfo-addr"
> +
> +/* Occupy a page of memory */
> +#define VMCOREINFO_FW_CFG_SIZE      4096
> +
> +/* allow space for OVMF SDT Header Probe Supressor */
> +#define VMCOREINFO_OFFSET           sizeof(AcpiTableHeader)
> +
> +#define VMCOREINFO(obj) OBJECT_CHECK(VMCoreInfoState, (obj), 
> VMCOREINFO_DEVICE)
> +
> +typedef struct VMCoreInfoState {
> +    DeviceClass parent_obj;
> +    uint8_t vmcoreinfo_addr_le[8];   /* Address of memory region */
> +    bool write_pointer_available;
> +} VMCoreInfoState;
> +
> +/* returns NULL unless there is exactly one device */
> +static inline Object *find_vmcoreinfo_dev(void)
> +{
> +    return object_resolve_path_type("", VMCOREINFO_DEVICE, NULL);
> +}
> +
> +void vmcoreinfo_build_acpi(VMCoreInfoState *vis, GArray *table_data,
> +                           GArray *vmci, BIOSLinker *linker);
> +void vmcoreinfo_add_fw_cfg(VMCoreInfoState *vis, FWCfgState *s, GArray 
> *vmci);
> +bool vmcoreinfo_get(VMCoreInfoState *vis, uint64_t *paddr, uint32_t *size,
> +                    Error **errp);
> +
> +#endif
> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> index 36a6cc450e..47043ade4a 100644
> --- a/hw/acpi/aml-build.c
> +++ b/hw/acpi/aml-build.c
> @@ -1561,6 +1561,7 @@ void acpi_build_tables_init(AcpiBuildTables *tables)
>      tables->table_data = g_array_new(false, true /* clear */, 1);
>      tables->tcpalog = g_array_new(false, true /* clear */, 1);
>      tables->vmgenid = g_array_new(false, true /* clear */, 1);
> +    tables->vmcoreinfo = g_array_new(false, true /* clear */, 1);
>      tables->linker = bios_linker_loader_init();
>  }
>  
> @@ -1571,6 +1572,7 @@ void acpi_build_tables_cleanup(AcpiBuildTables *tables, 
> bool mfre)
>      g_array_free(tables->table_data, true);
>      g_array_free(tables->tcpalog, mfre);
>      g_array_free(tables->vmgenid, mfre);
> +    g_array_free(tables->vmcoreinfo, mfre);
>  }
>  
>  /* Build rsdt table */
> diff --git a/hw/acpi/vmcoreinfo.c b/hw/acpi/vmcoreinfo.c
> new file mode 100644
> index 0000000000..0ea41de8d9
> --- /dev/null
> +++ b/hw/acpi/vmcoreinfo.c
> @@ -0,0 +1,208 @@
> +/*
> + *  Virtual Machine coreinfo device
> + *  (based on Virtual Machine Generation ID Device)
> + *
> + *  Copyright (C) 2017 Red Hat, Inc.
> + *  Copyright (C) 2017 Skyport Systems.
> + *
> + *  Authors: Marc-André Lureau <address@hidden>
> + *           Ben Warren <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +#include "qemu/osdep.h"
> +#include "hw/acpi/acpi.h"
> +#include "hw/acpi/aml-build.h"
> +#include "hw/acpi/vmcoreinfo.h"
> +#include "hw/nvram/fw_cfg.h"
> +#include "sysemu/sysemu.h"
> +#include "qapi/error.h"
> +
> +void vmcoreinfo_build_acpi(VMCoreInfoState *vis, GArray *table_data,
> +                           GArray *vmci, BIOSLinker *linker)
> +{
> +    Aml *ssdt, *dev, *scope, *method, *addr, *if_ctx;
> +    uint32_t vcia_offset;
> +
> +    g_array_set_size(vmci, VMCOREINFO_FW_CFG_SIZE);
> +
> +    /* Put this in a separate SSDT table */
> +    ssdt = init_aml_allocator();
> +
> +    /* Reserve space for header */
> +    acpi_data_push(ssdt->buf, sizeof(AcpiTableHeader));
> +
> +    /* Storage address */
> +    vcia_offset = table_data->len +
> +        build_append_named_dword(ssdt->buf, "VCIA");
> +    scope = aml_scope("\\_SB");
> +    dev = aml_device("VMCI");
> +    aml_append(dev, aml_name_decl("_HID", aml_string("QEMUVMCI")));
> +
> +    /* Simple status method to check that address is linked and non-zero */
> +    method = aml_method("_STA", 0, AML_NOTSERIALIZED);
> +    addr = aml_local(0);
> +    aml_append(method, aml_store(aml_int(0xf), addr));
> +    if_ctx = aml_if(aml_equal(aml_name("VCIA"), aml_int(0)));
> +    aml_append(if_ctx, aml_store(aml_int(0), addr));
> +    aml_append(method, if_ctx);
> +    aml_append(method, aml_return(addr));
> +    aml_append(dev, method);
> +
> +    /* the ADDR method returns two 32-bit words representing the lower and
> +     * upper halves of the physical address of the vmcoreinfo area
> +     */
> +    method = aml_method("ADDR", 0, AML_NOTSERIALIZED);
> +
> +    addr = aml_local(0);
> +    aml_append(method, aml_store(aml_package(2), addr));
> +
> +    aml_append(method, aml_store(aml_add(aml_name("VCIA"),
> +                                         aml_int(VMCOREINFO_OFFSET), NULL),
> +                                 aml_index(addr, aml_int(0))));
> +    aml_append(method, aml_store(aml_int(0), aml_index(addr, aml_int(1))));
> +    aml_append(method, aml_return(addr));
> +
> +    aml_append(dev, method);
> +    aml_append(scope, dev);
> +    aml_append(ssdt, scope);
> +
> +    g_array_append_vals(table_data, ssdt->buf->data, ssdt->buf->len);
> +
> +    /* Allocate guest memory */
> +    bios_linker_loader_alloc(linker, VMCOREINFO_FW_CFG_FILE, vmci, 4096,
> +                             false /* page boundary, high memory */);
> +
> +    /* Patch address of vmcoreinfo fw_cfg blob into the ADDR fw_cfg
> +     * blob so QEMU can read the info from there.  The address is
> +     * expected to be < 4GB, but write 64 bits anyway.
> +     * The address that is patched in is offset in order to implement
> +     * the "OVMF SDT Header probe suppressor"
> +     * see docs/specs/vmcoreinfo.txt for more details.
> +     */
> +    bios_linker_loader_write_pointer(linker,
> +        VMCOREINFO_ADDR_FW_CFG_FILE, 0, sizeof(uint64_t),
> +        VMCOREINFO_FW_CFG_FILE, VMCOREINFO_OFFSET);
> +
> +    /* Patch address of vmcoreinfo into the AML so OSPM can retrieve
> +     * and read it.  Note that while we provide storage for 64 bits, only
> +     * the least-signficant 32 get patched into AML.
> +     */
> +    bios_linker_loader_add_pointer(linker,
> +        ACPI_BUILD_TABLE_FILE, vcia_offset, sizeof(uint32_t),
> +        VMCOREINFO_FW_CFG_FILE, 0);
> +
> +    build_header(linker, table_data,
> +        (void *)(table_data->data + table_data->len - ssdt->buf->len),
> +        "SSDT", ssdt->buf->len, 1, NULL, "VMCOREIN");
> +    free_aml_allocator();
> +}
> +
> +void vmcoreinfo_add_fw_cfg(VMCoreInfoState *vis, FWCfgState *s, GArray *vmci)
> +{
> +    /* Create a read-only fw_cfg file for vmcoreinfo allocation */
> +    /* XXX: linker could learn to allocate without backing fw_cfg? */
> +    fw_cfg_add_file(s, VMCOREINFO_FW_CFG_FILE, vmci->data,
> +                    VMCOREINFO_FW_CFG_SIZE);
> +    /* Create a read-write fw_cfg file for Address */
> +    fw_cfg_add_file_callback(s, VMCOREINFO_ADDR_FW_CFG_FILE, NULL, NULL,
> +                             vis->vmcoreinfo_addr_le,
> +                             ARRAY_SIZE(vis->vmcoreinfo_addr_le), false);
> +}
> +
> +bool vmcoreinfo_get(VMCoreInfoState *vis,
> +                    uint64_t *paddr, uint32_t *size,
> +                    Error **errp)
> +{
> +    uint32_t vmcoreinfo_addr;
> +    uint32_t version;
> +
> +    assert(vis);
> +    assert(paddr);
> +    assert(size);
> +
> +    memcpy(&vmcoreinfo_addr, vis->vmcoreinfo_addr_le, 
> sizeof(vmcoreinfo_addr));
> +    vmcoreinfo_addr = le32_to_cpu(vmcoreinfo_addr);
> +    if (!vmcoreinfo_addr) {
> +        error_setg(errp, "BIOS has not yet written the address of %s",
> +                   VMCOREINFO_DEVICE);
> +        return false;
> +    }
> +
> +    cpu_physical_memory_read(vmcoreinfo_addr, &version, sizeof(version));
> +    if (version != 0) {
> +        error_setg(errp, "Unknown %s memory version", VMCOREINFO_DEVICE);
> +        return false;
> +    }
> +
> +    cpu_physical_memory_read(vmcoreinfo_addr + 4, paddr, sizeof(*paddr));
> +    *paddr = le64_to_cpu(*paddr);
> +    cpu_physical_memory_read(vmcoreinfo_addr + 12, size, sizeof(*size));
> +    *size = le32_to_cpu(*size);
> +
> +    return true;
> +}
> +
> +static const VMStateDescription vmstate_vmcoreinfo = {
> +    .name = "vmcoreinfo",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT8_ARRAY(vmcoreinfo_addr_le, VMCoreInfoState, 
> sizeof(uint64_t)),
> +        VMSTATE_END_OF_LIST()
> +    },
> +};
> +
> +static void vmcoreinfo_handle_reset(void *opaque)
> +{
> +    VMCoreInfoState *vis = VMCOREINFO(opaque);
> +
> +    /* Clear the guest-allocated address when the VM resets */
> +    memset(vis->vmcoreinfo_addr_le, 0, ARRAY_SIZE(vis->vmcoreinfo_addr_le));
> +}
> +
> +static void vmcoreinfo_realize(DeviceState *dev, Error **errp)
> +{
> +    if (!bios_linker_loader_can_write_pointer()) {
> +        error_setg(errp, "%s requires DMA write support in fw_cfg, "
> +                   "which this machine type does not provide",
> +                   VMCOREINFO_DEVICE);
> +        return;
> +    }
> +
> +    /* Given that this function is executing, there is at least one 
> VMCOREINFO
> +     * device. Check if there are several.
> +     */
> +    if (!find_vmcoreinfo_dev()) {
> +        error_setg(errp, "at most one %s device is permitted",
> +                   VMCOREINFO_DEVICE);
> +        return;
> +    }
> +
> +    qemu_register_reset(vmcoreinfo_handle_reset, dev);
> +}
> +
> +static void vmcoreinfo_device_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +
> +    dc->vmsd = &vmstate_vmcoreinfo;
> +    dc->realize = vmcoreinfo_realize;
> +    dc->hotpluggable = false;
> +}
> +
> +static const TypeInfo vmcoreinfo_device_info = {
> +    .name          = VMCOREINFO_DEVICE,
> +    .parent        = TYPE_DEVICE,
> +    .instance_size = sizeof(VMCoreInfoState),
> +    .class_init    = vmcoreinfo_device_class_init,
> +};
> +
> +static void vmcoreinfo_register_types(void)
> +{
> +    type_register_static(&vmcoreinfo_device_info);
> +}
> +
> +type_init(vmcoreinfo_register_types)
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 6b7bade183..7ac529680e 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -43,6 +43,7 @@
>  #include "sysemu/tpm.h"
>  #include "hw/acpi/tpm.h"
>  #include "hw/acpi/vmgenid.h"
> +#include "hw/acpi/vmcoreinfo.h"
>  #include "sysemu/tpm_backend.h"
>  #include "hw/timer/mc146818rtc_regs.h"
>  #include "sysemu/numa.h"
> @@ -2631,6 +2632,7 @@ void acpi_build(AcpiBuildTables *tables, MachineState 
> *machine)
>      GArray *tables_blob = tables->table_data;
>      AcpiSlicOem slic_oem = { .id = NULL, .table_id = NULL };
>      Object *vmgenid_dev;
> +    Object *vmcoreinfo_dev;
>  
>      acpi_get_pm_info(&pm);
>      acpi_get_misc_info(&misc);
> @@ -2680,6 +2682,12 @@ void acpi_build(AcpiBuildTables *tables, MachineState 
> *machine)
>          vmgenid_build_acpi(VMGENID(vmgenid_dev), tables_blob,
>                             tables->vmgenid, tables->linker);
>      }
> +    vmcoreinfo_dev = find_vmcoreinfo_dev();
> +    if (vmcoreinfo_dev) {
> +        acpi_add_table(table_offsets, tables_blob);
> +        vmcoreinfo_build_acpi(VMCOREINFO(vmcoreinfo_dev), tables_blob,
> +                              tables->vmcoreinfo, tables->linker);
> +    }
>  
>      if (misc.has_hpet) {
>          acpi_add_table(table_offsets, tables_blob);
> @@ -2856,6 +2864,7 @@ void acpi_setup(void)
>      AcpiBuildTables tables;
>      AcpiBuildState *build_state;
>      Object *vmgenid_dev;
> +    Object *vmcoreinfo_dev;
>  
>      if (!pcms->fw_cfg) {
>          ACPI_BUILD_DPRINTF("No fw cfg. Bailing out.\n");
> @@ -2897,6 +2906,11 @@ void acpi_setup(void)
>          vmgenid_add_fw_cfg(VMGENID(vmgenid_dev), pcms->fw_cfg,
>                             tables.vmgenid);
>      }
> +    vmcoreinfo_dev = find_vmcoreinfo_dev();
> +    if (vmcoreinfo_dev) {
> +        vmcoreinfo_add_fw_cfg(VMCOREINFO(vmcoreinfo_dev), pcms->fw_cfg,
> +                              tables.vmcoreinfo);
> +    }
>  
>      if (!pcmc->rsdp_in_ram) {
>          /*
> diff --git a/default-configs/arm-softmmu.mak b/default-configs/arm-softmmu.mak
> index 93e995d318..320dd3680d 100644
> --- a/default-configs/arm-softmmu.mak
> +++ b/default-configs/arm-softmmu.mak
> @@ -120,6 +120,7 @@ CONFIG_XIO3130=y
>  CONFIG_IOH3420=y
>  CONFIG_I82801B11=y
>  CONFIG_ACPI=y
> +CONFIG_ACPI_VMCOREINFO=y
>  CONFIG_SMBIOS=y
>  CONFIG_ASPEED_SOC=y
>  CONFIG_GPIO_KEY=y
> diff --git a/default-configs/i386-softmmu.mak 
> b/default-configs/i386-softmmu.mak
> index d2ab2f6655..df68628895 100644
> --- a/default-configs/i386-softmmu.mak
> +++ b/default-configs/i386-softmmu.mak
> @@ -59,3 +59,4 @@ CONFIG_SMBIOS=y
>  CONFIG_HYPERV_TESTDEV=$(CONFIG_KVM)
>  CONFIG_PXB=y
>  CONFIG_ACPI_VMGENID=y
> +CONFIG_ACPI_VMCOREINFO=y
> diff --git a/default-configs/x86_64-softmmu.mak 
> b/default-configs/x86_64-softmmu.mak
> index 9bde2f1c4b..e39ad5a680 100644
> --- a/default-configs/x86_64-softmmu.mak
> +++ b/default-configs/x86_64-softmmu.mak
> @@ -59,3 +59,4 @@ CONFIG_SMBIOS=y
>  CONFIG_HYPERV_TESTDEV=$(CONFIG_KVM)
>  CONFIG_PXB=y
>  CONFIG_ACPI_VMGENID=y
> +CONFIG_ACPI_VMCOREINFO=y
> diff --git a/docs/specs/vmcoreinfo.txt b/docs/specs/vmcoreinfo.txt
> new file mode 100644
> index 0000000000..36d5a39ab1
> --- /dev/null
> +++ b/docs/specs/vmcoreinfo.txt
> @@ -0,0 +1,138 @@
> +VIRTUAL MACHINE COREINFO DEVICE
> +===============================
> +
> +Copyright (C) 2017 Red Hat, Inc.
> +
> +This work is licensed under the terms of the GNU GPL, version 2 or later.
> +See the COPYING file in the top-level directory.
> +
> +===
> +
> +The VM coreinfo (vmcoreinfo) device is an emulated device which
> +exposes a 4k memory range to the guest to store various informations
> +useful to debug the guest OS.
> +
> +QEMU Implementation
> +-------------------
> +
> +The vmcoreinfo device is put in its own ACPI descriptor table, in a
> +Secondary System Description Table, or SSDT.
> +
> +The following is a dump of the contents from a running system:
> +
> +# iasl -p ./SSDT -d /sys/firmware/acpi/tables/SSDT
> +/*
> + * Intel ACPI Component Architecture
> + * AML/ASL+ Disassembler version 20160831-64
> + * Copyright (c) 2000 - 2016 Intel Corporation
> + *
> + * Disassembling to symbolic ASL+ operators
> + *
> + * Disassembly of /sys/firmware/acpi/tables/SSDT, Mon Apr 24 15:59:53 2017
> + *
> + * Original Table Header:
> + *     Signature        "SSDT"
> + *     Length           0x00000086 (134)
> + *     Revision         0x01
> + *     Checksum         0x5C
> + *     OEM ID           "BOCHS "
> + *     OEM Table ID     "VMCOREIN"
> + *     OEM Revision     0x00000001 (1)
> + *     Compiler ID      "BXPC"
> + *     Compiler Version 0x00000001 (1)
> + */
> +DefinitionBlock ("", "SSDT", 1, "BOCHS ", "VMCOREIN", 0x00000001)
> +{
> +    Name (VCIA, 0x3FFFF000)
> +    Scope (\_SB)
> +    {
> +        Device (VMCI)
> +        {
> +            Name (_HID, "QEMUVMCI")  // _HID: Hardware ID
> +            Method (_STA, 0, NotSerialized)  // _STA: Status
> +            {
> +                Local0 = 0x0F
> +                If (VCIA == Zero)
> +                {
> +                    Local0 = Zero
> +                }
> +
> +                Return (Local0)
> +            }
> +
> +            Method (ADDR, 0, NotSerialized)
> +            {
> +                Local0 = Package (0x02) {}
> +                Local0 [Zero] = (VCIA + 0x24)
> +                Local0 [One] = Zero
> +                Return (Local0)
> +            }
> +        }
> +    }
> +}
> +
> +
> +Design Details:
> +---------------
> +
> +QEMU must be able to read the contents of the device memory,
> +specifically when starting a memory dump.  In order to do this, QEMU
> +must know the address that has been allocated.
> +
> +The mechanism chosen for this memory sharing is writeable fw_cfg blobs.
> +These are data object that are visible to both QEMU and guests, and are
> +addressable as sequential files.
> +
> +More information about fw_cfg can be found in "docs/specs/fw_cfg.txt"
> +
> +Two fw_cfg blobs are used in this case:
> +
> +/etc/vmcoreinfo      - used to allocate memory range, read-only to the guest
> +/etc/vmcoreinfo-addr - contains the address of the allocated range
> +                     - writeable by the guest
> +
> +
> +QEMU sends the following commands to the guest at startup:
> +
> +1. Allocate memory for vmcoreinfo fw_cfg blob.
> +2. Write the address of vmcoreinfo into the SSDT (VCIA ACPI variable as
> +   shown above in the iasl dump).  Note that this change is not propagated
> +   back to QEMU.
> +3. Write the address of vmcoreinfo back to QEMU's copy of vmcoreinfo-addr
> +   via the fw_cfg DMA interface.
> +
> +After step 3, QEMU is able to read the contents of vmcoreinfo.
> +
> +The value of VCIA is persisted via the VMState mechanism.
> +
> +
> +Storage Format:
> +---------------
> +
> +The content is expected to use little-endian format.
> +
> +In order to implement an OVMF "SDT Header Probe Suppressor", the contents of
> +the vmcoreinfo blob has 36 bytes of padding:
> +
> ++-----------------------------------+
> +| SSDT with OEM Table ID = VMCOREIN |
> ++-----------------------------------+
> +| ...                               |       TOP OF PAGE
> +| VCIA dword object ----------------|-----> +---------------------------+
> +| ...                               |       | fw-allocated array for    |
> +| _STA method referring to VCIA     |       | "etc/vmcoreinfo"          |
> +| ...                               |       +---------------------------+
> +| ADDR method referring to VCIA     |       |  0: OVMF SDT Header probe |
> +| ...                               |       |     suppressor            |
> ++-----------------------------------+       | 36: uint32 version field  |
> +                                            | 40: info contents         |
> +                                            |     ....                  |
> +                                            +---------------------------+
> +                                            END OF PAGE
> +
> +Version 0 content:
> +
> + uint64 paddr:
> +  Physical address of the Linux vmcoreinfo ELF note.
> + uint32 size:
> +  Size of the vmcoreinfo ELF note.
> diff --git a/hw/acpi/Makefile.objs b/hw/acpi/Makefile.objs
> index 11c35bcb44..9623078f95 100644
> --- a/hw/acpi/Makefile.objs
> +++ b/hw/acpi/Makefile.objs
> @@ -6,6 +6,7 @@ common-obj-$(CONFIG_ACPI_MEMORY_HOTPLUG) += memory_hotplug.o
>  common-obj-$(CONFIG_ACPI_CPU_HOTPLUG) += cpu.o
>  common-obj-$(CONFIG_ACPI_NVDIMM) += nvdimm.o
>  common-obj-$(CONFIG_ACPI_VMGENID) += vmgenid.o
> +common-obj-$(CONFIG_ACPI_VMCOREINFO) += vmcoreinfo.o
>  common-obj-$(call lnot,$(CONFIG_ACPI_X86)) += acpi-stub.o
>  
>  common-obj-y += acpi_interface.o
> -- 
> 2.13.1.395.gf7b71de06